Filter member

ABSTRACT

A filter member which comprises one layer of deodorizing filter  1 , which is composed of a reticulated filter substrate and a deodorizing agent adhering to the surface of its skeletons, and one or two layers of dust collecting filter  2   a  and  2   b  laminated on any one side or both sides thereof, with the resulting laminate being pleated.

TECHNICAL FIELD

The present invention relates to a filter member which possesses afunction of both deodorization and dust collection, and moreparticularly, to a filter member which excels in ability to eliminateodors and to collect fine dust while keeping its performance withoutappreciable pressure loss and clogging.

BACKGROUND ART

A variety of filters have found use in many fields. They include filtersto remove trace gas from a clean room, filters for air cleaning, airconditioning, and ventilation, and filters that admit outside air intothe automotive cabin (cabin filter). Filters are used also in fuel cellswhich are attracting attention recently. They are required to removeimpurities from air (as an oxygen source) being supplied to the fuelcell. Thus, applications of filters are expanding more and more.

Under these circumstances, an ability to both collect dust and removegaseous components is required of filters for air cleaners, airconditioners, ventilators, and automotive air ducts to admit outside airinto the cabin.

Meanwhile, fuel cells are expected to be a promising technology to copewith global warming. For their operation, fuel cells need air as anoxygen source to be supplied to the oxygen electrode. Unfortunately, aircontains sulfur compounds and organic compounds detrimental to thecatalytic action in fuel cells. For stable output over a long period oftime, fuel cells should be supplied with as pure air as possible afterremoval of impurities from outside air. This calls for filters with highdeodorizing (gas removing) performance and high dust collectingperformance. Moreover, filters for fuel cells should have low pressureloss as well as high deodorizing and dust collecting performance becauseauxiliary equipment (such as blowers) should run with low energyconsumption for improved energy conversion efficiency.

It has been common practice to collect comparatively fine dust smallerthan 10 μm (referred to as fine dust hereinafter) by using filters madeof polypropylene fiber, polyester fiber, polyamide fiber, glass fiber,or the like. Such filters are nonwoven fabrics produced from polymers byspun bonding or melt blowing. There is known a charged filter which ishighly capable of collecting fine dust by Coulomb force due to charge onan easily chargeable non-polar polymer such as polypropylene, asdisclosed in Japanese Patent Publication Nos. Sho 56-47299, Sho57-14467, and Hei 5-15485, and Japanese Patent Laid-open Nos. Sho61-46215, Hei 4-213335, and Hei 7-227510.

There are other filters such as net-like ones formed from polypropyleneor polyethylene resin and those of three-dimensionally reticulatedpolyurethane foam, which are used for collection of comparatively coarsedust larger than 10 μm (referred to as coarse dust hereinafter).

Unfortunately, the former fibrous filters are liable to clogging, whichdecreases efficiency soon, despite their good ability to collect finedust, and the latter net-like filters lack an ability to collect finedust.

There has been proposed a filter to achieve dust removal anddeodorization simultaneously which is formed into a desired shape from adeodorizing agent and a dust removing material by using a binder(Japanese Patent Laid-open No. Hei 8-117524). This filter, however, isnot necessarily good in deodorizing performance because it merelypermits a limited amount of deodorizing agent to be incorporatedthereinto so that it keeps its low initial pressure loss. Another filterfor simultaneous deodorization and dust removal is one which is a simplelaminate composed of a deodorizing layer and a dust collecting layer. Ithas the disadvantage of being poor in deodorizing and dust removingperformance per unit amount of pressure loss.

There has been proposed another type of filter which is composed of twolayers of nonwoven fabrics (both capable of dust collection) laminatedon top of the other, with deodorizing particles attached to the insideof one layer by means of a hot-melt adhesive. Unfortunately, this filteris inherently liable to clogging if it is intended mainly to collectfine dust, and this prevents incorporation with a sufficient amount ofdeodorizing agent. Conversely, the filter will be very poor in abilityto collect fine dust if it is sufficiently incorporated with adeodorizing agent.

As explained above, conventional filters cannot exhibit both dustcollecting ability and deodorizing ability when they are used in areas,such as ventilation, air conditioning, automobiles, and fuel cells,where an increase in initial pressure loss after filter mounting or anincrease in pressure loss due to clogging with dust is not permissiblebecause it lowers the blowing capacity. They do not meet all therequirements.

There has been proposed a pleated filter member which is expected tohave both dust collecting ability and deodorizing ability. It is made ofpolyurethane foam with three-dimensionally reticulated skeletons free ofcell membrane, and it is used as the base of deodorizing filters or dustcollecting filters. Although it collects coarse dust efficiently withoutbecoming clogged easily and it is also capable of deodorization, it islimited in the amount of deodorizing agent to be incorporated thereintobecause it increases in initial pressure loss if it is designed forefficient collection of fine dust.

DISCLOSURE OF THE INVENTION

It is an object of the present invention, which was completed in view ofthe foregoing, to provide a high-performance filter member which iscapable of collecting both coarse dust and fine dust, permitsincorporation with a sufficient amount of deodorizing agent fordeodorization to a desired extent, and achieves dust collection anddeodorization in a well-balanced manner at a low pressure loss withoutbecoming clogged easily.

After their extensive studies carried out to achieve the above-mentionedobject, the present inventors found that a high-performance filtermember can be obtained if one layer of deodorizing filter, which iscomposed of a reticulated filter substrate and a deodorizing agentadhering to the surface of its skeletons, is laminated with one or twolayers of dust collecting filter, and the resulting laminate is entirelypleated. The resulting filter member accomplishes collection of bothfine and coarse dust and deodorization equally well at a low pressureloss without clogging. Such performance has never been attained by theconventional technology. The present invention was completed on thebasis of this finding.

Thus, the present invention is directed to a filter member whichincludes one layer of deodorizing filter, which is composed of areticulated filter substrate and a deodorizing agent adhering to thesurface of its skeletons, and one or two layers of dust collectingfilter laminated on any one side or both sides thereof, with theresulting laminate being pleated.

Incidentally, the term “deodorization” used in this specificationimplies removal of any gaseous components as well as removal of odorcomponents.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partly enlarged perspective view showing a filter memberpertaining to one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description of the present invention will be given below.

As shown in FIG. 1, the filter member according to the present inventionis typically composed of a deodorizing filter layer 1 and one or twodust collecting filter layers 2 a and 2 b laminated on any one side orboth sides thereof (the latter case is shown in FIG. 1), with theresulting laminate being pleated.

The layer of deodorizing filter 1 is prepared from a reticulated filtersubstrate and a deodorizing agent adhering to the surface of theskeletons thereof. The reticulated filter substrate is highlybreathable, permits a large amount of deodorizing agent to adherethereto, and retains sufficient strength after pleating.

The reticulated filter substrate for the deodorizing filter 1 may bemade of polypropylene, polyethylene, polyester, polyamide, or the like,without specific restrictions. The reticulated filter substrate iscomposed of strands usually forming squares, rectangles, hexagons,rhombuses, or the like without specific restrictions. Strands may formtwo or more of these figures in combination. The spacing and thicknessof strands should be properly established in consideration of theinitial pressure loss desired, the particle size of the deodorizingagent, and the strength of the pleats, although they are notspecifically restricted. Preferably, spacing of strands is usually 1 to15 mm, particularly 2 to 6 mm, so that the reticulated filter substratehas a low pressure loss and a high capacity for incorporation withdeodorizing agent and retains its strength after pleating. Adequatethickness of strands is usually 0.1 to 2 mm, particularly 0.3 to 1 mm,so that the reticulated filter substrate keeps its low pressure loss andretains its strength at the sharp ridges of pleats.

The reticulated filter substrate may be primed so that the strandsurface is coated easily with a binder (mentioned later). Primingincludes dipping in a resin solution (such as epoxy and polyacrylicacid) and corona discharge treatment which physically roughens thestrand surface. The reticulated filter substrate should preferablyundergo preliminary biaxial orientation so that it will not deform dueto tension and heat during binder coating mentioned later and pleating.

The deodorizing agent to be applied to the reticulated filter substratemay be selected properly without specific restrictions according to theintended purpose. Its typical examples include petroleum pitch-basedactivated carbon, coconutshell-based activated carbon, pellet-formedactivated carbon, wood-based activated carbon, natural or syntheticzeolite, SiO₂, ZnO, TiO₂, silica gel, activated clay, cation or anionexchange resin, manganese oxide, and alumina. They may be used alone orin combination with one another. In addition, the deodorizing agentshould preferably be in spherical or spheroidal shape with a low fluidresistance because it greatly affects the pressure loss of the resultingfilter member.

The deodorizing agent (adsorbent) variously affects the performance offine dust collection depending on its type selected. The one which givesoff little dust is desirable. Its typical examples include petroleumpitch-based or coconutshell-based activated carbon and zeolite whosespherical particles are coated with a porous polymeric layer ofpolyester, polytetrafluoroethylene (PTFE), polypropylene, or the like.

Of the above-mentioned deodorizing agents, activated carbons with alarge specific surface area for adsorption are desirable from thestandpoint of deodorizing performance; however, they are disadvantageousfor removal of gaseous components with a low molecular weight and astrong polarity because they depend mainly on van der Waals force fortheir adsorption. They should preferably be incorporated with anadequate additive for improvement in deodorizing performance.

The additive includes chemicals which neutralize acids or bases, orcondense aldehyde and amine by Schiff reaction. The former isexemplified by phosphoric acid, hydrochloric acid, malic acid, etc. (asacidic additives) and sodium carbonate, sodium metasilicate, KOH, NaOH,etc. (as basic additives). The latter is exemplified byaminophenylacetic acid, aminobenzoic acid, aminobenzenesulfonic acid,etc.

The deodorizing filter layer 1 as a constituent of the filter member ofthe present invention is composed of the reticulated filter substrateand the deodorizing agent attached to the skeletons thereof. There areno specific restrictions as to the method of attaching particles ofdeodorizing agent to the reticulated filter substrate. This object isachieved usually by forming a binder layer on the surface of theskeletons of the reticulated filter substrate and then attaching theparticulate deodorizing agent to the binder layer. Desirable examples ofthe binder include polyamide, polyolefin, ethylene-vinyl acetatecopolymer, synthetic rubber, polyurethane, and acrylic resin in the formof hot melt or non-solvent emulsion.

The layers of dust collecting filter 2 a and 2 b which are laminatedonto the layer of deodorizing filter mentioned above are notspecifically restricted so long as they are capable of collecting dust.Desirable ones include a fibrous filter or a polyurethane foam free ofcell membrane.

The fibrous material may be formed from any material, such aspolypropylene, polyethylene, polyester, and glass, which are notspecifically restricted. They may be used alone or in combination withone another. For desired effects, their fiber diameter should preferablybe 1 to 100 μm, particularly 10 to 50 μm, and their basis weight shouldbe 20 to 200 g/m², particularly 35 to 75 g/m². An excessively largefiber diameter is disadvantageous for the ability to mechanicallycollect dust, and conversely an excessively small fiber diameterpromotes clogging. An excessively large basis weight increases pressureloss, and conversely an excessively small basis weight is detrimental tothe dust collecting performance.

The fibrous filter mentioned above may be prepared in the form ofmelt-blow nonwoven fabric, spun-bond nonwoven fabric, glass fibernonwoven fabric, or their composite nonwoven fabric from theabove-mentioned fibers. Nonwoven fabrics with needle punching arepreferable.

The three-dimensionally reticulated polyurethane foam (free of cellmembrane) as the dust collecting filter should preferably be apolyether-based or polyester-based polyurethane foam. Its typicalexample includes “Everlight SF” commercially available from BridgestoneKaseihin Seizo Co., Ltd.

Incidentally, the fibrous filter or the dust collecting filter layers 2a and 2 b of polyurethane foam should preferably be given antistatictreatment, although not mandatory.

There are no specific restrictions as to the method of laminating thedust collecting filter layers 2 a and 2 b onto the deodorizing filterlayer 1. Lamination may be accomplished by using an adhesive, such aspolyamide, polyolefin, ethylene-vinyl acetate copolymer, syntheticrubber, polyurethane, and acrylic resin in the form of hot melt ornon-solvent emulsion. Bonding with a hot melt in the form of nonwovenfabric or a hot melt spread like a spider's web is desirable from thestandpoint of keeping pressure loss low and preventing the gas adsorbingperformance from deterioration.

Good bonding with an adhesive can be achieved between the deodorizingfilter layer 1 and the dust collecting filter layers 2 a and 2 b if thereticulated filter substrate as a constituent of the deodorizing filterlayer 1 is previously given priming treatment such as corona dischargeand resin coating as mentioned above. This priming treatment improvesaffinity for the adhesive, thereby ensuring firm adhesion.

The filter member of the present invention includes one layer ofdeodorizing filter and one or two layers of dust collecting filterlaminated onto any one side or both sides of the layer of deodorizingfilter. A filter member of three-layer structure as shown in FIG. 1 isdesirable although it is not mandatory. It includes one layer ofdeodorizing filter 1 and two layers of dust collecting filter 2 a and 2b laminated onto both sides thereof. In this case, it is desirable toplace a coarse dust collecting filter 2 a on the obverse side (intowhich the raw gas flows) and to place a fine dust collecting filter 2 bon the reverse side (from which the filtrate leaves). This arrangementis appropriate from the standpoint of avoiding clogging.

In other words, a desirable way to effectively protect the filter fromclogging in principle is to permit the filter to catch dust particlesvarying in size sequentially in the order of decreasing particle size.This object is achieved lo if the dust collecting filter has a densitygradient. According to the present invention, a desirable densitygradient can be readily established by laminating the layer ofdeodorizing filter 1 with the coarse dust collecting filter 2 a on itsupstream side and with the fine dust collecting filter 2 b on itsdownstream side.

This object is achieved if the coarse dust collecting filter 2 a isformed from the three-dimensionally reticulated polyurethane foam freeof cell membrane (mentioned above) and the fine dust collecting filter 2b is formed from the fibrous filter (mentioned above), particularlypolypropylene-based electret nonwoven fabric which excels in fine dustcollecting performance. Any other construction may also be possible.

Incidentally, the filter member of the present invention takes on apleated form, and pleating can be accomplished in the usual way by usingany known pleating machine.

In what follows, the present invention will be described in more detailwith reference to Examples and Comparative Examples which are notintended to restrict the scope of the invention.

EXAMPLE Example 1

A reticulated filter substrate, 300 mm wide and 2000 mm long, was cutout of plastic netting “Nisseki Conwed-net” (from Nisseki Sheet PalletSystem Co., Ltd.) as specified below.

-   -   Basis weight: 49 g/m²    -   Average spacing of strands: 4 mm in both longitudinal and        lateral directions    -   Average net thickness: about 0.7 mm in the vicinity of the nodal        point of longitudinal and lateral strands    -   Average strand thickness: about 0.3 mm (both longitudinal and        lateral strands)

The above-mentioned reticulated filter substrate was dipped in a binderof acrylic-based emulsion (“EW-2500” from Soken Chemical & EngineeringCo., Ltd.), with pickup being 30 g/m² (on dry basis). Dipping wasfollowed by complete drying at 80° C., so that a binder layer was formedon the surface of strands. To the binder layer were attached (with theaid of its tackiness) spherical particles of petroleum pitch-basedactivated carbon (“G-70R” from Kureha Chemical Industry Co., Ltd.). Thusthere was obtained a flat reticulated deodorizing filter layer whichcarries 500 g of activated carbon per square meter.

Then, to each side of the deodorizing filter layer was laminated adust-collecting filter layer, with an interlayer placed between them.Lamination was accomplished by hot pressing at 130° C. for 20 seconds.The interlayer is a polyamide-based hot melt nonwoven fabric cut in thesame size as above (“PA-150” from Diabond Industry Co., Ltd.). Thedust-collecting filter layer, which is placed on the obverse side (orupstream side) of the deodorizing filter, is for coarse dust collection,and it is a three-dimensionally reticulated polyether-based polyurethanefoam free of cell membrane (“Everlight SF FQ-40^(1t)” from BridgestoneCorp.), measuring 1 mm thick, 300 mm wide, and 2000 mm long. Thedust-collecting filter layer, which is placed on the reverse side(downstream side) of the deodorizing filter, is for fine dustcollection, and it is a polypropylene-based electret nonwoven fabric(“SB050N” from Toray Fine Chemicals Co., Ltd.). Thus there was obtaineda filter sheet of three-layer structure.

The filter sheet was pleated (30 mm high) by using a pleating machine ofreciprocating type. The pleats were fixed at a pitch of 12 mm with apolyester nonwoven fabric, 1.5 mm thick, having a basis weight of 100g/m² and a 50 μm thick coating of polyolefin hot melt. Thus there wasobtained a pleated filter member which carries about 2500 g of activatedcarbon per square meter of projected area.

Example 2

The same procedure as in Example 1 was repeated to give a flatdeodorizing filter layer, which carries 550 g of activated carbon persquare meter, except that the reticulated filter substrate was replacedby a plastic netting “Nisseki Conwed-net ON6200” (from Nisseki SheetPallet System Co., Ltd.) as specified below.

-   -   Basis weight: 34 g/m²    -   Average spacing of strands: 3.5 mm in longitudinal direction and        4 mm in lateral direction    -   Average net thickness: about 0.45 mm in the vicinity of the        nodal point of longitudinal and lateral strands    -   Average strand thickness: about 0.3 mm (longitudinal strands)        and 0.15 mm (lateral strands)

Then, to both sides of the deodorizing filter layer were laminateddust-collecting filter layers (one for coarse dust collection and onefor fine dust collection) in the same manner as in Example 1.Theresulting laminate was pleated. Thus there was obtained a pleated filtermember which carries about 2750 g of activated carbon per square meterof projected area.

The filter members obtained in Examples 1 and 2 were tested forbreathability, fine dust collecting performance, life to clogging, andcoarse dust collecting performance in the following manner by using avertical wind tunnel (250 by 250 mm inside) specified by the Japan AirCleaning Association. For comparison, the same test as above wasperformed on a cabin filter which is composed of two layers ofpolypropylene nonwoven fabrics bonded together with an adhesive, withcrashed activated carbon held between them. The results of tests areshown in Table 1.

Details of filter member for comparison are as follows.

Details of Filter Member for Comparison

-   -   Shape: pleated (height: 29 mm, pitch: 6.5 mm, expansion ratio:        approx. 9)

Amount of activated carbon: about 300 g/m² (flat area), and about 2700g/m² (projected area)

[Test Methods]

Breathability

Expressed in terms of initial pressure loss (in Pa) at a wind velocityof 3.5 m/s.

Fine Dust Collecting Performance

Expressed in terms of the ratio of airborne dust (0.3 to 0.5 μm)collected at a wind velocity of 1.5 m/s.

Life to Clogging

Expressed in terms of the amount of dust collected per unit area of thesample filter member until the initial pressure loss increases by 150 Pawhen the sample filter member collects dust (15 kinds specified in JIS)continuously at a rate of 0.6 g/min from air flowing at a wind velocityof 3.5 m/s.

Coarse Dust Collecting Performance

Expressed in terms of the ratio (%) of dust retained per unit area ofthe sample filter member until the initial pressure loss increases by150 Pa when the sample filter member collects dust (15 kinds specifiedin JIS) continuously at a rate of 0.6 g/min from air flowing at a windvelocity of 3.5 m/s.

TABLE 1 Comparative Example 1 Example 2 Example Amount of activatedcarbon in flat  500  550  300 area (g/m²) Expansion ratio of pleats ×5×5 ×9 Amount of activated carbon in 2500 2750 2700 projected area (g/m²)Initial pressure loss at a wind  103  101  115 velocity of 3.5 m/min(Pa) Fine dust collecting performance in  23.5% 23.00% 3.50% terms ofratio of collection of airborne dust, 0.3 to 0.5 μm, (%) Life toclogging in terms of  368  357  302 amount of dust collected for initialpressure loss to increase by 150 Pa (g/m²) Coarse dust collectingperformance 94.50%   93%   90% in terms of ratio of retained dust (%)

It is noted from Table 1 that the filter member according to the presentinvention produces the following effects (1) to (4) in contrast to theconventional one.

-   -   (1) Lower pressure loss for the same amount of deodorizing        agent.    -   (2) Better fine dust collecting performance (about 6.5 times or        above) for the same amount of deodorizing agent.    -   (3) Equal or better coarse dust collecting performance for the        same amount of deodorizing agent.    -   (4) Well-balanced effective improvement in fine dust collecting        performance, deodorizing performance, and clogging prevention        without appreciable increase in pressure loss.

As mentioned above, the filter member according to the present inventioncan collect both coarse dust and fine dust and adsorb odor with asufficient amount of deodorizing agent in a well-balanced manner withlittle liability to clogging at a reasonably low pressure loss.

1. A filter member: comprising one layer of deodorizing filter, which iscomposed of a reticulated filter substrate having a skeleton comprisingstrands and a deodorizing agent adhered to a surface of the skeleton,and at least one layer of dust collecting filter laminated on at leastone side thereof, with the resulting laminate being pleated, whereinsaid reticulated filter substrate is formed from one of polypropylene,polyethylene, polyester, and polyamide and said deodorizing agent usedfor said layer of deodorizing filter comprises spherical or spheroidalparticles formed of at least one of petroleum pitch-based activatedcarbon, coconutshell-based activated carbon, pellet-formed activatedcarbon, wood-based activated carbon, natural or synthetic zeolite, SiO₂,ZnO, TiO₂, silica gel, activated clay, cation or anion exchange resin,manganese oxide, and alumina.
 2. A filter member as defined in claim 1,wherein said layer of deodorizing filter and said layer of dustcollecting filter are bonded together with an adhesive.
 3. A filtermember as defined in claim 2, wherein said adhesive is selected from agroup of polyamide, polyolefin, ethylene-vinyl acetate copolymer,synthetic rubber, polyurethane, and acrylic resin in the form of hotmelt or non-solvent emulsion.
 4. A filter member as defined in claim 2,wherein said adhesive is a hot melt in the form of nonwoven fabric or ahot melt spread like a spider's web.
 5. A filter member as defined inclaim 2, wherein said reticulated filter substrate as a constituent ofsaid layer of deodorizing filter is primed by corona discharge treatmentor resin coating to improve affinity for said adhesive.
 6. A filtermember as defined in claim 1, wherein said reticulated filter substrateas a constituent of said layer of deodorizing filter has undergonebiaxial orientation.
 7. A filter member as defined in claim 1, whereinsaid strands have a spacing of 1 to 15 mm and a thickness of 0.1 to 2mm.
 8. A filter member as defined in claim 1, wherein said strands formone or more shapes of squares, rectangles, hexagons, and rhombuses.
 9. Afilter member as defined in claim 1, wherein said deodorizing agent isone which is incorporated with a chemical which reacts with aldehydesthrough Schiff reaction.
 10. A filter member as defined in claim 1,wherein said deodorizing agent is one which is incorporated with achemical which neutralizes an acid or base.
 11. A filter member asdefined in claim 1, wherein said surface of said skeleton comprises abinder layer and said deodorizing agent adheres to said binder layer.12. A filter member as defined in claim 11, wherein said binder layer isselected from a group of polyamide, polyolefin, ethylene-vinyl acetatecopolymer, synthetic rubber, polyurethane, and acrylic resin in the formof hot melt or non-solvent emulsion.
 13. A filter member as defined inclaim 1, wherein said layer of dust-collecting filter is formed from afibrous filter.
 14. A filter member as defined in claim 13, wherein saidfibrous filter is composed of one or more kinds of fibers selected froma group of polypropylene fiber, polyethylene fiber, polyester fiber, andglass fiber, and these fibers have a fiber diameter of 1 to 100 μm. 15.A filter member as defined in claim 13, wherein said fibrous filter is afabric having a basis weight of 20 to 200 g/m².
 16. A filter member asdefined in claim 13, wherein said fibrous filter is one or more kinds ofcomposite nonwoven fabrics selected from a group of melt blow nonwovenfabric, spun bond nonwoven fabric, and glass fiber nonwoven fabric, andthe nonwoven fabric has undergone needle punching.
 17. A filter memberas defined in claim 1, wherein said layer of dust-collecting filter is athree-dimensionally reticulated polyether-based or polyester-basedpolyurethane foam free of cell membrane.
 18. A filter member as definedin claim 1, wherein said layer of dust-collecting filter has undergoneantistatic treatment.
 19. A filter member as defined in claim 1, whereinsaid layer of deodorizing filter is laminated with a layer of filter tocollect coarse dust on the obverse side thereof and with a layer offilter to collect fine dust on the reverse side thereof, and raw gasenters the filter layer on the obverse side and leaves from the filterlayer on the reverse side, thereby removing dust and gaseous components.20. A filter member as defined in claim 19, wherein said layer of filterto collect coarse dust is formed from a three-dimensionally reticulatedpolyether-based or polyester-based polyurethane foam free of cellmembrane, and said layer of filter to collect fine dust is formed from afibrous filter.
 21. A filter member: comprising one layer of deodorizingfilter, which is composed of a reticulated filter substrate having askeleton and a deodorizing agent adhered to a surface of the skeleton,and at least one layer of dust collecting filter laminated on at leastone side thereof, with the resulting laminate being pleated, whereinsaid deodorizing agent used for said layer of deodorizing filtercomprises spherical or spheroidal particles formed of at least one ofpetroleum pitch-based activated carbon, coconutshell-based activatedcarbon, pellet-formed activated carbon, wood-based activated carbon,natural or synthetic zeolite, SiO₂, ZnO, TiO₂, silica gel, activatedclay, cation or anion exchange resin, manganese oxide, and alumina,wherein said layer of deodorizing filter and said layer of dustcollecting filter are bonded together with an adhesive, and wherein saidreticulated filter substrate as a constituent of said layer ofdeodorizing filter is primed by corona discharge treatment or resincoating to improve affinity for said adhesive.